1. Field of the Invention
The present invention relates to a method for automatic determination of the validity or invalidity of input by keys arranged next to each other in a keypad or keyboard.
2. Description of the Related Art
Keypads, touch pads or keyboards are increasingly used to control various electronic units. These electronic units include computers, mobile phones, organizers, remote control panels and many other devices. They are designed ever smaller in connection with electronic unit miniaturization. A natural limit to miniaturization of a keyboard, touch screen or keypad comprising individual keys or touch sensors results from the size of the adult fingers, which are still able to operate the keyboard. The probability is very high with too small keys that two or more keys or touch sensors are operated at the same time instead of only one key, which leads to indefinite or unclear input.
This problem can be addressed by connecting the keys with an electronic controller, which shuts off the associated electronic unit when several keys or touch sensors are operated, pressed or contacted at the same time.
U.S. Pat. No. 5,973,621 describes a keypad comprising a plurality of adjacent key switches, arranged in a controllable flat pattern. The key switches are mechanical keys in the case of this patent. In order for an adult with large fingers to operate the miniaturized keyboard or keypad, key legends or characters are arranged in the intervening spaces between the keys, instead, as is common, on the individual keys. Particularly each key legend or character is associated with four or six adjacent keys, which together correspond to a fingertip area. This presupposes that the center of the fingertip area is applied at the intersection of the intervening spaces.
If necessary, additional key legends or characters can also be associated with individual keys. The keypad keys are then divided into two categories for evaluation of key inputs: keys, which are correlated with a single key legend or character, and other keys, which are only associated with an intervening space correlation. Only key inputs in which key switches or keys of one category or the other are pressed are determined to be valid
In another type of analysis disclosed in U.S. Pat. No. 5,973,621 components of the signals originating from individual keys are differentiated according to intensity. Then the signal components are tested after ascertaining an intensity maximum for the signal component of one of the keys to determine whether sufficiently remote keys operated at the same time produce no signal component.
In GB 2 263 184 A it is proposed to arrange the keys so close to each other that usually more than one key is simultaneously operated. From the first how many and which auxiliary keys must be pressed with each main key is given. The electronics are designed so that each time whether all the associated auxiliary keys are operated with the main key is tested and, only if that is the case, is the appropriate key input correlated to operation of the main key. The electronics does not detect whether or not all associated auxiliary keys are operated together with the main key. However this case can occur especially when an operator with different sized fingers uses the keypad. For this case it is suggested that keypads with different dimensions should be provided.